Term
| Humoral immunity involves which cells? |
|
Definition
| B cells and CD4+ TH2 cells |
|
|
Term
| Cell mediated immunity involves which cells? |
|
Definition
|
|
Term
| Secretion of IFN upregulates what? What causes it’s secretion? |
|
Definition
| MHC Class I molecules and viral infections (respectively) |
|
|
Term
| What do cytokines upregulate? |
|
Definition
| MHC II. Those produced by CD4+ TH1 cells produce cytokines which active macrophages and upregulate the expression of Fc receptors on macrophages, NK cell and neutrophils. Cytokines recruit neutrophils and other leukocytes to the infected areas |
|
|
Term
| What does TLR4 recognize, stimulate, and do? |
|
Definition
| LPS, NF-κB, upregulates cytokine production and other molecules for B/T cell activation |
|
|
Term
| What amino acids comprise the hinge region? |
|
Definition
|
|
Term
| Where is the hinge region found, and what isotypes is it absent? |
|
Definition
| Between CH1 and CH2…not found in IgM or IgE |
|
|
Term
| Where does pepsin cleave an antibody? |
|
Definition
| Below the S-S bond at the hinge, producing 1 fragment (Fab)2 |
|
|
Term
| What isotypes is the J chain associated with? |
|
Definition
| Polymeric → IgA and IgM (not hexameric IgM though) |
|
|
Term
| What is J chain required for? |
|
Definition
| Polymerization and interacts with poly-Ig receptor for transcytosis |
|
|
Term
| Which domains of the Ab do not interact? |
|
Definition
| CH2 due to steric hinderence of CHO |
|
|
Term
| Which part of the Ab makes contact with epitopes? |
|
Definition
| The hypervariable regions of the variable domain, AKA CDR’s (complement determining regions) |
|
|
Term
| Which isotypes have subclasses and how many? |
|
Definition
|
|
Term
| Where is IgM found as a monomer? |
|
Definition
| As a BCR on mature B cells |
|
|
Term
| What isotype is the most efficient in activating the complement pathway? |
|
Definition
|
|
Term
| What is the only isotpye made by the fetus? |
|
Definition
| IgM until 4-6 months of age when they can make other Ig’s |
|
|
Term
| What is the primary structural characteristic used to determine the different subclass of IgG? |
|
Definition
|
|
Term
| Why does IgG have such a long half life? |
|
Definition
| Due to the recycling of it |
|
|
Term
| What is the only isotype able to cross the placental barrier? |
|
Definition
|
|
Term
| Which IgG subclasses activate complement? |
|
Definition
|
|
Term
| When does the production of IgG take place in an infant? |
|
Definition
|
|
Term
| When can IgG participate in ADCC? |
|
Definition
| When bound by Fc receptors on NK cells |
|
|
Term
| What is the best opsonin? |
|
Definition
|
|
Term
| Which IgA subclass is predominate in serum? |
|
Definition
|
|
Term
| Which IgA subclass is directed towards polysaccharide epitopes? Protein epitopes? |
|
Definition
|
|
Term
| Which Ig is the most abundant made? Which is the most abundant in tissues and serum? |
|
Definition
| IgA (>60% of the 3g of antibody made per day) and IgG respectively |
|
|
Term
| What is the most predominate isotype found in secretions and mucosal surfaces? |
|
Definition
|
|
Term
| What isotypes are found in gingival cervicular fluid? |
|
Definition
| Monomeric IgA, IgG and IgM |
|
|
Term
| Monomeric IgA is mostly found in … |
|
Definition
|
|
Term
|
Definition
| In secretions in it’s dimer form (secretory component helps protect it from cleavage by enzymes) |
|
|
Term
| Where is secretory IgA mostly secreted from? |
|
Definition
| Minor and major salivary glands |
|
|
Term
|
Definition
| Bound to surface of mast cells, basophils and eosinophils by its Fc(epsilon) receptor |
|
|
Term
| What does IgE do when it binds an antigen? |
|
Definition
| Degranulation releasing granules |
|
|
Term
| Which isotype plays a role in protection against parasites? |
|
Definition
| IgE by binding epitopes of the parasite and releasing granules to kill parasite directly |
|
|
Term
| What is the function of IgD? |
|
Definition
| B cell activation as a BCR |
|
|
Term
| What happens to a B cell is IgD is missing? |
|
Definition
| Self reactive B cells can enter lymphoid organ and proliferate |
|
|
Term
| Hematopoetic stem cells can become… |
|
Definition
| Stem cells, myeloid cells, lymphoid cells or erythroid cells |
|
|
Term
| Name some cells from the myeloid lineage |
|
Definition
| Monocytes/macrophages, dendritic cells, and granulocytes (basophil, eosinophil, mast cell, neutrophil) |
|
|
Term
| Name some cells from the lymphoid cell lineage |
|
Definition
|
|
Term
| Name some cells from the erythroid lineage |
|
Definition
|
|
Term
| What surface receptors do monocytes/macrophages have? |
|
Definition
CR3 – complement receptor 3 for Cb3
Fc – for Fc portion of IgG and IgE antibodies |
|
|
Term
| Macrophages can be activated from their resting state by: |
|
Definition
| PAMPs (LPS, mannose) Opsinization IFN-γ (produced by Th1, CD8+, and NK cells) |
|
|
Term
| What are the functions of macrophages? |
|
Definition
| Phagocytosis, antigen presenation, production of soluble mediators, and ADCC |
|
|
Term
| What cytokines does a macrophages secrete when it phagocytoses a pathogen? |
|
Definition
|
|
Term
| When a target is coated with IgG, what do macrophages do? |
|
Definition
| Kill the target directly without phagocytosis via ADCC |
|
|
Term
|
Definition
| The release of enzymes causing damage to nearby neighbors of infected cells (“innocent bystanders”) |
|
|
Term
| What is the best phagocyte we have? |
|
Definition
|
|
Term
| What is the functions of neutrophils? |
|
Definition
| Phagocytosis and cytokine production |
|
|
Term
| What are defensins and what cells secrete these? |
|
Definition
| Defensins poke holes in membranes to kill phagocytosed pathogens. Neutrophils release these. |
|
|
Term
| What cells have an oxidative burst? |
|
Definition
| Neutrophils and macrophages |
|
|
Term
| What cytokines do neutrophils produce? |
|
Definition
| Proinflammatory cytokines – IL-1, IL-6, TNF-α, and IL-8 (IL-8 is the only additional one it secretes vs. macrocrphages) |
|
|
Term
| what cytokines do dendritic cells produce? |
|
Definition
|
|
Term
| what are the functions of dendritic cells? |
|
Definition
| phagocytosis, antigen presentation, negative selection (where they present self antigens to developing T cells in thymus), and cytokine production |
|
|
Term
| where are follicular dendritic cells found? |
|
Definition
| germinal cetners and follicles of lymphoid tissues |
|
|
Term
| T or F: Follicular dendritic cells are phagocytic |
|
Definition
| Flase, they are NOT phagocytic |
|
|
Term
| T or F: Dendritic cells present to T cells and Follicular Dendritic Cells present to B cells |
|
Definition
|
|
Term
| What is the function of FDC's? |
|
Definition
| They bind the whole antigen-antibody complex via the Fc portion of the antibody, and present the "unprocessed" antigen to B cells in lymphoid germinal centers |
|
|
Term
| T or F: FDCs express MHC molecules |
|
Definition
| False, they do not express MHC molecules |
|
|
Term
| CD4+ T cells differentiate into ____ who's effector function is to _______ |
|
Definition
T helper cells.
Produce cytokines |
|
|
Term
| CD8+ T cells differentiate into ______ whos effector function is to ____ |
|
Definition
| T cytotoxic cells who kill infected host cells or tumor cells |
|
|
Term
| Are CD4 and CD8 expressed exclusively or mutually on T cells? |
|
Definition
|
|
Term
| what cytokines inhibit TH2 differentiation? |
|
Definition
| IFN-γ, produced by TH1 cells |
|
|
Term
| What cytokines prevent differentiation of TH1 cells? |
|
Definition
| IL-4 and IL-10 (produced by TH2 cells) |
|
|
Term
| Which cytokines favor TH1 differentiation? |
|
Definition
| IL-12 (produced by DCs, macrophages, and neutrophils) |
|
|
Term
| TH1 cells produce what cytokines? |
|
Definition
|
|
Term
| TH1 cells stimulate which T cells? |
|
Definition
|
|
Term
| TH1 cells stimulate isotype switching in B cells to produce which isotypes? |
|
Definition
|
|
Term
| TH2 cells produce what cytokines? |
|
Definition
|
|
Term
| What cells do TH2 cells stimulate? |
|
Definition
| B cells to produce antibodies |
|
|
Term
| Which isotypes does TH2 cells stimulate B cells to produce? |
|
Definition
|
|
Term
| The presentation and severity of disease is determined by what? |
|
Definition
| the predominance of TH1 vs TH2 phenotypes |
|
|
Term
| What is the function of CD8+ T cells? |
|
Definition
| to kill target cells through release of cytotoxic enzymes such as host cells with intracellular pathogens, tumor cells or incompatible grafted/transplanted tissues |
|
|
Term
| Naive B cells have which BCRs present? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| CD40 interacts with _____ to _____. |
|
Definition
| CD40L on T cells to provide second activating signal for B cells and signals the B cell to undergo isotype switching |
|
|
Term
| CD80 or CD87 are found where? |
|
Definition
|
|
Term
| CD80/86 interact with _____ to _____. |
|
Definition
| CD28 on T cells to provide second activating signal for T cell |
|
|
Term
| What are the functions of B cells? |
|
Definition
| Production of antibodies (plasma cells), immunologic memory (memory B cells), antigen presentation (antigen binds to BCR and is phagocytosed and presented to T cell via MHC molecule) |
|
|
Term
| NK cells are part of (adaptive or innate) immune system |
|
Definition
|
|
Term
| how do we identify NK cells? |
|
Definition
| Fc-γ receptor and IL-2R receptor (receptor for IL-2 that proliferates at low levels of IL-2). Do NOT have TCR or BCR |
|
|
Term
| what is the function of NK cells? |
|
Definition
| direct killing of target cells by release of cytotoxic enzymes and production of IFN-γ |
|
|
Term
| IFN-γ has what functions? |
|
Definition
| antiviral effects (protects cell) and stimulates cytotoxic activity of Tc cells and macrophages |
|
|
Term
|
Definition
| Fc-γ receptors on surface bind IgG coated antigen |
|
|
Term
| Where is the site that blood-borne pathogens are processed and presented? |
|
Definition
|
|
Term
| what ways can a antigen enter a lymph node? |
|
Definition
| via the lymph either as soluble antigen or within phagocyte |
|
|
Term
|
Definition
| specialized mucosal epithelial cells that delivery pathogens across mucosa into MALT |
|
|
Term
| the majority of lymphocytes are found where? |
|
Definition
|
|
Term
| what do naive T cells have that allows them to enter lymph nodes? |
|
Definition
|
|
Term
| Once a T cell is activated in a lymph node, what happens? |
|
Definition
| it loses its L selectin receptors and will not reenter other lymph nodes, but leave the lymph node and reenter circulation to find tissues that are colonized by infectious microorganisms |
|
|
Term
| Where is the one place in the body where lymphocytes do not circulate through secondary lymphoid tissue in both blood and lymph? |
|
Definition
|
|
Term
|
Definition
| small fatty acid that has antibacterial and chemotactic properties |
|
|
Term
| what substances lower the pH of skin to 4? |
|
Definition
| sebum and fatty acids (some bacteria use sebum as a nutrient) |
|
|
Term
| what do keratinocytes do in regards of the immune system? |
|
Definition
| produce cytokines that stimulate cutaneous inflammation and produce chemokines that attract monocytes to site of injury |
|
|
Term
|
Definition
| glycoproteins, proteoglycans and enzymes |
|
|
Term
| what does normal flora do to protect us? |
|
Definition
| prevents binding by occupying sites, utilizes nutrients that bacteria would normally use, and secretes bacteriocins that are toxic to bacteria |
|
|
Term
| where are lysozymes and lactoperoxidases found? |
|
Definition
|
|
Term
| where are anti-microbial peptides (defensins) found and what are they most effective against? |
|
Definition
| found in mucosal secretions and cytoplasmic granules of phagocytes. effective against gram negative bacterial and enveloped viruses |
|
|
Term
| what does lactoferrin do? transferrin? |
|
Definition
| both bind free iron. lactoferrin in mucosal secretions and transferrin in the blood...making it unavailable to bacteria |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| what is the function of inflammation? |
|
Definition
| remove or limit spread of injurious agent, clean up the damage, repair tissue |
|
|
Term
| inflammation involves what? |
|
Definition
| vasodilation and vascular permeability (from cytokines, kinins and histamine), phagocyte migration (neutrophils in 30-60min, monocytes in 4-6 hours), increased phagocytosis, cytokines upregulate adhesion molecules to guide neutrophils/monocytes where to go, and plasmin to remodel/repair |
|
|
Term
| Mannose binding lectin binds what and activates what? |
|
Definition
| mannose on bacertia/fyeast to activate the lectin pathway of the complement system |
|
|
Term
| C-reactive protein binds what? and activates what? |
|
Definition
| binds LPS on bacteria/fungal walls, acts as opsonin and initiates classical complement pathway (by binding C1q) |
|
|
Term
|
Definition
|
|
Term
| what does the leader sequence do and what is it comprised of? |
|
Definition
| it traffics the protein to a cytoplasmic compartment and is comprised of mainly hydrophobic amino acids |
|
|
Term
| what does the leader sequence do and what is it comprised of? |
|
Definition
| it traffics the protein to a cytoplasmic compartment and is comprised of mainly hydrophobic amino acids |
|
|
Term
| the variable light chain is constructed from what genes? |
|
Definition
variable gene encodes the first 95 AAs (CDR1, CDR2 and first part of CDR3)
joining gene encodes the last 13 AA (last part of DCR3) |
|
|
Term
| what genes encode the variable Heavy chain? |
|
Definition
variable gene (CDR1 and CDR2)
diversity gene (first part of CDR3)
joining gene (last part of CDR3) |
|
|
Term
| what are recombination signal sequences |
|
Definition
| DNA sequences that regulate the recombination of genes for Variable Light and Variable Heavy chains |
|
|
Term
| how does κ light chain rearrangement differ from λ light chain? |
|
Definition
Both chains have leader sequences directly preceding the gene. However in the κ chain, there are J-κ genes located just downstream of the V-κ genes, and upstream from the C-κ genes. λ light chains have the V-genes upstream followed by sequences of JC-genes (4 of them) to provide 4 different λ-light chains.
In the lambda chain, the C-lambda genes precede the 4 J-lambda genes, so there are 4 different types of lambda L chains) |
|
|
Term
| What is the gene rearrangement sequence in the κ light chains regarding VJC? |
|
Definition
|
|
Term
| What is the gene rearrangement in the λ light chains regarding VJC? |
|
Definition
|
|
Term
| after rearrangement of the κ or λ light chains, what do they do? |
|
Definition
| they travel to the ER where they join the H chains to make a complete Ig molecule |
|
|
Term
|
Definition
| located within introns, they dictate the distance and rotation of the DNA when brining antibody genes together and prevent V genes from recombining with J genes (in H Chains) |
|
|
Term
| What do recombinase activating genes do? |
|
Definition
| binds to RSS's and creates nicks in the DNA to remove the intervening DNA and allow the two genes to become juxtaposed |
|
|
Term
| Which spacer (12 or 23) is associated with the V-κ gene? The J-κ? |
|
Definition
|
|
Term
| which spacer (12 or 23) is associated with the V-λ gene? the J-λ gene? |
|
Definition
|
|
Term
| what is combinatorial diversity? |
|
Definition
| random arrangement of VDJ genes of H chains and VJ genes of L chains |
|
|
Term
| what is combinatorial association? |
|
Definition
| random association of H and L chains |
|
|
Term
| when does junctional diversity occur? |
|
Definition
| during Ig gene rearrangement |
|
|
Term
| Junctional diversity only affects which CDR? |
|
Definition
|
|
Term
| What are the 3 functions of Junctional diversity? |
|
Definition
| P-nucleotide addition, Junctional flexibility, and N-Nucleotide addition |
|
|
Term
| N-Nucleotide addition occurs due to what enzyme? |
|
Definition
| TdT, terminal deoxynucleotidyl transferase...which can add to an exposed end 1-10 nucleotides, which then a polymerase can use to fill in the gap. |
|
|
Term
| Where does N-Nucleotide addition occur? |
|
Definition
| only in H chains since TdT is not present in pre-B cells during L chain rearrangement |
|
|
Term
| what is the only mechanism to generate diversity that occurs after gene rearrangement and after exposure to an antigen? |
|
Definition
| Somatic Hypermutation SHM |
|
|
Term
|
Definition
| introduces point mutations into the V regions |
|
|
Term
| What CDRs are affected by SHM? |
|
Definition
|
|
Term
| What is affinity maturation? |
|
Definition
| produce antibodies with a higher affinity for the antigen |
|
|
Term
| Where does SHM and affinity maturation take place? |
|
Definition
| in the follicle of the secondary lymphoid organ |
|
|
Term
| What happens during Pro-B cell stage? |
|
Definition
RAG is upregulated to initiate VDJ rearrangement
VDJ rearrangement in variable heavy chain occurs
expression of Ig(alpha) and Ig(beta) |
|
|
Term
| what happens during the LARGE pre-B cell stage? |
|
Definition
synthesis and expression of μ chain with surrogate light chains 14.1 and V preB
Igα and Igβ signal successful rearrangement of H chain genes, and H chains undergo several rounds of cell division to increase number |
|
|
Term
| what do Igβ and Igα do in a mature B cell? |
|
Definition
| signal to the nucleus that a antigen binded to the BCR |
|
|
Term
| where are Igα and Igβ located? |
|
Definition
| associated with membrane Ig molecules in ALL cells of the B lineage, until it becomes a plasma cell |
|
|
Term
| What happens during the small pre-B cell stage? |
|
Definition
| Upregulation of RAG genes cause L chain gene rearrangement. Expression of surrogate L chain genes (14.1 and V preB) cease. More μ chain is made but stored in ER. |
|
|
Term
| what is the pre-B cell receptor complex? |
|
Definition
| μ chain, 14.1, V preB, Igα, Igβ |
|
|
Term
| What separates immature B cells from small pre-B cells? |
|
Definition
| The L chains pair with the μ chains and form a complete BCR (IgM + Igα and Igβ). |
|
|
Term
| before leaving the bone marrow, what do immature B cells have to do? |
|
Definition
| interact with self antigen for self tolerance and either undergo 1. apoptosis 2. become anergic or 3. attempt receptor editing |
|
|
Term
| what happens to the immature B cells after leaving the bone marrow? |
|
Definition
| acquires additional surface (IgD, CR1, CR2, CD40 and L-selectin) molecules to classify it as a mature B lymphocyte |
|
|
Term
| A immature B cell expresses what? a mature B cell? |
|
Definition
| IgM + Igα and Igβ. IgM and IgD + Igα and Igβ |
|
|
Term
| What does B cell activation by TI antigens NOT result in? |
|
Definition
|
|
Term
| Do antibodies undergo affinity maturation when activated by a TD antigen? |
|
Definition
| yes, they do NOT under affinity maturation when activated by a TI antigen |
|
|
Term
| B cell's required second signal to become activated into plasma cells comes from? |
|
Definition
|
|
Term
|
Definition
| TI-1 antigens that tend to be components of bacterial cell walls and can activate B cells through mitogen receptors regardless of antigen specificity and do not require BCR cross linking |
|
|
Term
| _____ can only activate antigen specific mature B cells |
|
Definition
|
|
Term
| Which provide a greater titer of antibodies? TI or TD antigens? |
|
Definition
|
|
Term
|
Definition
| large structures with repeating epitopes that binding of the many epitopes by BCR cross linking generates a very strong intracellular activation signal. |
|
|
Term
| what happens to people who can not respond to TI-2 antigens? |
|
Definition
| highly susceptible to infection by encapsulated bacteria and suffer from immunodeficiency called Wiskott-Aldrich syndrome |
|
|
Term
| The bulk of pathogen specific antibody responses are produced through what kind of antigen activation? where does this occur? |
|
Definition
| TD activating B cells in secondary lymphoid tissues |
|
|
Term
| what region of the lymph node are DCs retained so that their processed antigens are able to be sampled by the T cells passing through? |
|
Definition
|
|
Term
| what is the second required signal for B cell activation? |
|
Definition
| CD40 and CD40L interaction |
|
|
Term
| after a B cell is activated in the lymph node, where does it migrate? |
|
Definition
| to the follicle of the lymph node so that a germinal center develops |
|
|
Term
| where does clonal expansion, SHM and affinity maturation, isotype switching, and differentiation into plasma/memory cells happen for B cells? |
|
Definition
| in the germinal center of the B cell while in the follicle of the lymph node???? |
|
|
Term
| how long do plasma cells secrete antibodies? |
|
Definition
| 2-4 weeks and then undergo apoptosis |
|
|
Term
| what does activation of a CD4+ T cell do? |
|
Definition
| release cytokines that help activate B cell and lead to further differentiation of the activated T cell to a TH1 or TH2 cell |
|
|
Term
| what does the CD40-CD40L interaction do? |
|
Definition
| increases expression of MHC II, CD80 and CD86 on B cells |
|
|
Term
| Which molecule is upregulated first when CD40 and CD40L interact? |
|
Definition
|
|
Term
| CD80 preferentially binds what? what does it do and what does this stimulate? |
|
Definition
| CTLA4, and when it does, it terminates activation of the T cell. Can bind CD28 and when it does, it provides 2nd activation signal for T cell. Stimulates a TH1 response |
|
|
Term
| How does hyper-IgM syndrome happen? |
|
Definition
| When people who lack functional CD40L undergo very little isotype switching, making them more susceptible to certain types of infectious agents |
|
|
Term
| What does CD86 preferentially bind to? what happens when it binds and what does it stimulate? |
|
Definition
| prefers CD28, and provides 2nd activation signal for T cells and stimulates a TH2 response |
|
|
Term
|
Definition
| found on T cells and when it interacts with CD80 or CD86 on B cells, it provides the required co-stimulatory signal for full activation of the T cell |
|
|
Term
|
Definition
| found on T cells, and is upregulated upon T cell activation. It interacts with CD80 and CD86 and terminates activation of the T cell |
|
|
Term
| isotype switching involves specialized sequences called _____ and are found ______ |
|
Definition
| switch regions. upstream (5') of each CH gene (except δ) |
|
|
Term
| What two steps are required for the development of T cells? |
|
Definition
| 1. Selection FOR self MHC and 2. selection AGAINST those having receptors recognizing self-antigens |
|
|
Term
| what is MHC restriction (aka self-MHC restriction)? |
|
Definition
| the ability of T cells to recognize only our own MHC molecules |
|
|
Term
| what type of TCR is more numerous and more diverse than the other form? |
|
Definition
|
|
Term
| which type of TCR is found in specific tissues and interacts with the non-classical MHC molecules such as CD1? |
|
Definition
|
|
Term
| The V region of which TCR genes are encoded by V & J genes? |
|
Definition
|
|
Term
| the V region of which TCR genes are encoded by V, D & J genes? |
|
Definition
|
|
Term
| which TCR genes do not follow allelic exclusion? |
|
Definition
| α...so it is possible to have two different TCRs on the same T cell with two different α chains and the same β chain |
|
|
Term
| The TCR genes begin rearrangement with which genes? |
|
Definition
|
|
Term
| How does a T cell prevent it from having both types of TCR present on it? |
|
Definition
| the δ genes are located between the α genes so that when α genes rearrange, the δ genes are deleted and prevents a T cell from having both TCR types |
|
|
Term
| Which genes DO NOT undergo SMH, isotype switching, or combinatorial association? |
|
Definition
|
|
Term
| In what ways do TCR genes generate diversity? |
|
Definition
| Combinatorial Diversity (any V with any D with any J, etc.) and Junctional diversity (P-nucleotide addition, etc) |
|
|
Term
| Which portion of the TCR interacts with the MHC molecules and diversifies at a lower rate? |
|
Definition
|
|
Term
| Where does most of the diversity take place in the TCR's CDR? |
|
Definition
| in the portion that interacts with epitopes, CDR3 |
|
|
Term
| How does the TCR create additional diversity in the CDR3 region? |
|
Definition
| more J genes available and the 12 bp and 23 bp spacers are arranged so that the V can skip the D genes to rearrange directly with the J genes, or there can be multiple D genes involved (VJ or VDDJ, etc) |
|
|
Term
| T or F: TCRs follow the 23/12 rule |
|
Definition
|
|
Term
| which genes do TCRs begin rearrangement with? |
|
Definition
| D-J genes, i.e. the β and δ genes |
|
|
Term
| What is positive selection? |
|
Definition
| Where thymocytes (double positive, CD4+ and CD8+) are subjected to thymic stromal cells expressing MHC Class I and II molecules on their surface and eliminating those thymocytes who do not interact with the MHC molecule via apoptosis. If MHC Class I interacts with CD8 co-receptor, then CD4 disappears, and vice versa. |
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Term
| what kind of cells do CD4+ become? CD8+? |
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Definition
CD4+ = cytokine secreting cells
CD8+ = cytotoxic effector cells |
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Term
| What is negative selection and where does it take place? |
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Definition
| presentation of self-peptides complexed to either MHC Class I or II molecules, to the the single positive thymocytes by the DCs & macrophages at the cortico-medullary junction of the thymus. Those that bind strongly will die by apoptosis, and those that bind weakly will survive because they recognize the MHC but not the peptide. They will exit the thymus as a mature, single-positive T cell. |
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Term
| What is different about γδ TCR thymocytes? |
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Definition
| they exit thymus without being "educated", following the rearrangement of their genes. Some express CD8 co-receptors but not CD4 receptors. |
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Term
| where are CD3 and ζ (zeta) chains found? what do they do? |
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Definition
| they are made during the T cell development and form part of the pre-TCR and full TCR complexes. Upon successful rearrangement of the β chain genes, they are chaperoned by the CD3 and zeta chains to the surface to for the pre-TCR complex. |
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Term
| what does the pre-TCR complex consist of? |
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Definition
| β chain, CD3 and ζ chains |
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Term
| what is a full TCR complex? |
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Definition
| αβ TCR, CD3 and ζ chains) on the surface |
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